The direct effect of stratospheric variability on the tropospheric circulation

Recent observational and numerical evidence suggests that stratospheric processes play an important role in driving tropospheric climate variability on both intraseasonal and climate change timescales. In this talk, I will argue that the amplitude of the tropospheric response to stratospheric variability is consistent with the direct effect of anomalous wave driving at stratospheric levels. The result contradicts the current orthodoxy that internal tropospheric dynamics are required to explain the observed amplitudes at tropospheric levels. It is further argued that the ~two month persistence of the tropospheric response to stratospheric variability is consistent with the direct effect of anomalous radiative cooling at stratospheric levels. Implications for the interpretation of recent climate change are discussed.